TY - JOUR
T1 - Predominance of anaerobic, spore-forming bacteria in metabolically active microbial communities from ancient Siberian permafrost
AU - Liang, Renxing
AU - Lau, Maggie
AU - Vishnivetskay, Tatiana
AU - Lloyd, Karen G.
AU - Wang, Wei
AU - Wiggins, Jessica
AU - Miller, Jennifer
AU - Pfiffner, Susan
AU - Rivkina, Elizaveta M.
AU - Onstott, Tullis C.
N1 - Publisher Copyright:
© 2019 American Society for Microbiology.
PY - 2019
Y1 - 2019
N2 - The prevalence of microbial life in permafrost up to several million years (Ma) old has been well documented. However, the long-term survivability, evolution, and metabolic activity of the entombed microbes over this time span remain underexplored. We integrated aspartic acid (Asp) racemization assays with metagenomic sequencing to characterize the microbial activity, phylogenetic diversity, and metabolic functions of indigenous microbial communities across a ~0.01- to 1.1-Ma chronosequence of continuously frozen permafrost from northeastern Siberia. Although Asp in the older bulk sediments (0.8 to 1.1 Ma) underwent severe racemization relative to that in the youngest sediment (~0.01 Ma), the much lower D-Asp/ L-Asp ratio (0.05 to 0.14) in the separated cells from all samples suggested that indigenous microbial communities were viable and metabolically active in ancient permafrost up to 1.1 Ma. The microbial community in the youngest sediment was the most diverse and was dominated by the phyla Actinobacteria and Proteobacteria. In contrast, microbial diversity decreased dramatically in the older sediments, and anaerobic, spore-forming bacteria within Firmicutes became overwhelmingly dominant. In addition to the enrichment of sporulation-related genes, functional genes involved in anaerobic metabolic pathways such as fermentation, sulfate reduction, and methanogenesis were more abundant in the older sediments. Taken together, the predominance of spore-forming bacteria and associated anaerobic metabolism in the older sediments suggest that a subset of the original indigenous microbial community entrapped in the permafrost survived burial over geological time.
AB - The prevalence of microbial life in permafrost up to several million years (Ma) old has been well documented. However, the long-term survivability, evolution, and metabolic activity of the entombed microbes over this time span remain underexplored. We integrated aspartic acid (Asp) racemization assays with metagenomic sequencing to characterize the microbial activity, phylogenetic diversity, and metabolic functions of indigenous microbial communities across a ~0.01- to 1.1-Ma chronosequence of continuously frozen permafrost from northeastern Siberia. Although Asp in the older bulk sediments (0.8 to 1.1 Ma) underwent severe racemization relative to that in the youngest sediment (~0.01 Ma), the much lower D-Asp/ L-Asp ratio (0.05 to 0.14) in the separated cells from all samples suggested that indigenous microbial communities were viable and metabolically active in ancient permafrost up to 1.1 Ma. The microbial community in the youngest sediment was the most diverse and was dominated by the phyla Actinobacteria and Proteobacteria. In contrast, microbial diversity decreased dramatically in the older sediments, and anaerobic, spore-forming bacteria within Firmicutes became overwhelmingly dominant. In addition to the enrichment of sporulation-related genes, functional genes involved in anaerobic metabolic pathways such as fermentation, sulfate reduction, and methanogenesis were more abundant in the older sediments. Taken together, the predominance of spore-forming bacteria and associated anaerobic metabolism in the older sediments suggest that a subset of the original indigenous microbial community entrapped in the permafrost survived burial over geological time.
KW - Ancient permafrost
KW - Aspartic acid racemization
KW - Microbial activity
KW - Sporeforming bacteria
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U2 - 10.1128/AEM.00560-19
DO - 10.1128/AEM.00560-19
M3 - Article
C2 - 31152014
AN - SCOPUS:85070116094
SN - 0099-2240
VL - 85
JO - Applied and Environmental Microbiology
JF - Applied and Environmental Microbiology
IS - 15
M1 - e00560-19
ER -